Field of the Disclosure
The present disclosure relates to a piezoelectric blower that transports gas.
Description of the Related Art
There are various types of piezoelectric blowers for cooling heat sources in electronic devices or for supplying oxygen required to generate power in fuel cells. One example is a piezoelectric blower 900 disclosed in Patent Document 1.
FIG. 9 is a cross-sectional view of the piezoelectric blower 900 in Patent Document 1. The piezoelectric blower 900 includes an inner casing 1 and an outer casing 5.
The inner casing 1 includes a diaphragm 21 to which a piezoelectric element 20 and an intermediate plate 22 are bonded, a frame plate portion 13 bonded to the diaphragm 21, and a top plate portion 10 bonded to the frame plate portion 13. In the inner casing 1, the diaphragm 21, the frame plate portion 13, and the top plate portion 10 define a blower space 3.
The top plate portion 10 has a first vent 11 communicating between the inside and outside of the blower space 3 and includes a plurality of supporting portions 4 fixed on the outer casing 5. The plurality of supporting portions 4 elastically support the inner casing 1 with respect to the outer casing 5.
The outer casing 5 covers the inner casing 1 such that a gap is disposed therebetween. An airway 6 is defined between the outer casing 5 and the inner casing 1. The outer casing 5 has a second vent 8 in a location opposed to the first vent 11.
The piezoelectric element 20 has a first principal surface 20A and a second principal surface 20B opposed to the first principal surface 20A. An electrode for driving the piezoelectric element 20 is disposed on each of the first principal surface 20A and the second principal surface 20B. The top plate portion 10 includes an electrode terminal 83 protruding from the outer casing 5. The electrode terminal 83 and the electrode on the first principal surface 20A of the piezoelectric element 20 are electrically connected to each other with the intermediate plate 22 and the inner casing 1 disposed therebetween. An electrode terminal 82 is disposed on the bottom surface of the outer casing 5. The electrode terminal 82 and the electrode on the second principal surface 20B of the piezoelectric element 20 are electrically connected to each other with a lead wire 79 disposed therebetween.
In the above configuration, when an alternating drive voltage is applied from the electrode terminals 82 and 83 to the piezoelectric element 20, the piezoelectric element 20 expands and contracts, and the expansion and contraction of the piezoelectric element 20 causes the diaphragm 21 to bend and vibrate. The bending vibration of the diaphragm 21 changes the volume of the blower space 3 periodically.
Specifically, when the diaphragm 21 bends toward the piezoelectric element 20, the volume of the blower space 3 increases. With this, gas outside the piezoelectric blower 900 is sucked into the blower space 3 through the airway 6 and the first vent 11.
Then, when the diaphragm 21 bends toward the blower space 3, the volume of the blower space 3 reduces. With this, gas inside the blower space 3 is discharged from the second vent 8 through the airway 6 and the first vent 11. At this time, the air outside the piezoelectric blower 900 is drawn through the airway 6 by the air discharged from the blower space 3 and is discharged from the second vent 8. Thus, the quantity of flow of the air discharged from the second vent 8 increases by the quantity of flow of the air drawn from the outside.
Patent Document 1: International Publication No. 2009/148008